DC power converters convert power at one DC voltage to power at another DC voltage. An important application of DC converters is in the field of photovoltaics in which an unregulated DC voltage produced by a solar panel is converted into regulated DC power. A popular DC converter architecture is the flyback converter. The flyback architecture uses a switched transformer coupled between the converter's input and output circuits. A primary switch, in series with the primary winding of the transformer, controls the connection of the primary winding to an input voltage source. In a flyback converter, energy is taken from the input power source and stored in the magnetisation inductance of the transformer during a first portion of the flyback cycle, and is then transferred to the converter output during the second portion of the flyback cycle. A “clamp” circuit is frequently coupled across the primary winding of the transformer. The clamp circuit is designed to limit the voltage stress on the primary switch when it opens. A clamp circuit provides a temporary current path for primary current and limits the voltages across the primary switch. Clamp circuits can be implemented in a variety of ways.